Calcium hydroxide [Ca(OH)2], a by-product of the acetylene production process, is a potential liming source for acid agricultural soils. The material as generated has a moisture content of 80%, which decreases to about 50% after settling in a collecting pond. Air dried Ca(OH)2 (2.63% moisture), ground to pass a 300 µm sieve, had a CaCO3 equivalent of 120%, Commercial CaCO3 (1.53% moisture) had a pure CaCO3 equivalent of 84%. Both liming sources were evaluated in laboratory incubation studies using four acid soils; Corozal clay (Ultisol), Mariana (Inceptisol), Bayamón (Oxisol) and Alonso (Ultisol). The industrial waste [Ca(OH)2] was as effective as CaCO3 in neutralizing soil acidity. An application of 8.0 meq/100g of both liming sources increased the pH of Mariana soil from 4.65 to 6.07, Corozal soil from 4.13 to 4.92 and Alonso soil from 4.74 to 6.48. The pH of Bayamón soil increased from 4.39 to 6.65 with the application of 8.0 meq of CaCO3; however, the same amount of Ca(OH)2 increased the pH to 6.92. Exchangeable Al3+ levels were close to zero in Mariana, Bayamón and Alonso soils at pH values between 6.0-6.3. Exchangeable Al3+ in Coroza! soil decreased from 934.37 mg/kg to 269.79 mg/kg as the pH increased from 4.13 to 4.92. in a short term incubation experiment (5 days), Ca(OH)2 reacted faster than CaCO3 to neutralize soil acidity. Samples of Mariana, Alonso and Bayamón soils treated with 8.0 meq/100g of Ca(OH)2 reached pH values around 6,00 after one day of incubation, whereas CaCO3-treated samples reached similar pH values only after the second or third day of incubation.